People
who are physically fit and active have fewer and milder colds,
indicates research published online in the British Journal of Sports
Medicine.

The
US researchers base their findings on 1,000 adults up to the age of 85
whose respiratory health was tracked for 12 weeks during the autumn and
winter of 2008.

Six
out of 10 participants were women, and 4 out of 10 were aged between 18
and 39; 40%were middle aged, and one in four were aged 60 and older.

All
the participants reported back on how frequently they took aerobic
exercise and rated their fitness levels using a validated 10-point
scoring system. They were also asked about lifestyle, diet and recent
stressful events, as these can all affect immune system response.

The
number of days with cold symptoms varied considerably between winter
and autumn, with an average of 13 days in the winter and 8 days in the
autumn.

Being
older, male, and married, seemed to reduce the frequency of colds, but
after taking account of other influential factors, the most significant
factors were perceived fitness and the amount of exercise taken.

The
number of days with symptoms among those who said they were physically
active on five or more days of the week and felt fit was almost half
(43% to 46% less) that of those who exercised on only one or fewer days
of the week.

The severity of symptoms fell by 41% among those who felt the fittest and by 31% among those who were the most active.

In
the US, an average adult can expect to have a cold two to four times a
year, while children can catch between half a dozen and 10 colds a
year, on average, all of which costs the US economy around $40 billion
dollars.

Bouts
of exercise spark a temporary rise in immune system cells circulating
around the body, say the authors. Although these levels fall back
within a few hours, each bout is likely to enhance surveillance of
harmful viruses and bacteria, so reducing the number and severity of
infections, such as the common cold.

For more information on the BMJ-British Medical Journal, visit www.bmj.com.